Differences in monoterpene emission characteristics after ozone exposure between three clones representing major gene pools of Cryptomeria japonica

Abstract

　Tropospheric ozone (O₃) concentration has been increasing. The aim of this study was to compare the effect of O₃ exposure on monoterpene emission rate and the components of Japanese cedar (Cryptomeria japonica) between three major gene pools identified by population genetic structure analysis. At the O₃-FACE (Free-Air O₃ and CO₂ Enrichment) facility, 1-year saplings of three clones of Japanese cedar (Donden, Kawazu, and Yakushima) were exposed to ambient double concentrations of O₃. After 15 months of O₃ exposure experiment, monoterpene emission characteristics were evaluated by branch enclosure method using cutting samples of current-year leaves. Basal biogenic volatile organic compound emission rate (E_s) was higher in the O₃ exposure plots, and two-way analysis of variance revealed an effect of the O₃ exposure (p<0.05) and an interaction between the O₃ exposure and clone (p<0.05). Especially, high E_s values were observed in the Yakushima after the O₃ exposure. In addition, the coefficient β related to temperature sensitivity increased in the O₃ exposure plots (p<0.05). Our findings supported the fact that there are large inter-clone variations in C. japonica. It is important to evaluate the differences in clones considering the genetic diversity and to clarify the mechanism of the differences after long-term moderate O₃ exposure.